The present invention relates to a conference system which utilizes a plurality of time division digital switches.
In recent years there has grown a demand for conference systems through a plurality of telephones. Conventionally conference systems of this kind generally have an arrangement in which transmitting and receiving highways are formed on a time division basis and communication signals on the receiving highway are conference-operated and delivered out in predetermined time slots through the transmitting highway. With this kind of conventional systems, however, it is very difficult to determine dynamically and flexibly the number of groups participating in a conference and the number of participants. As a solution to this problem, there has been proposed a method which employs a buffer memory in an input/output part associated with the highways, as disclosed in Japanese Pat. Pub. Disc. Nos. 28608/80 and 57072/82 gazettes. This method has solved the problem of flexibility. On the other hand, however, the above method requires the buffer memory and its control circuit to operate at high speed, leading to the defect of limitations on the semiconductor elements that can be used.
Moreover, in this kind of system heretofore employed, since a plurality of conference trunks are provided and exclusive channels are allocated to them, channels equal in number to (the number of conference trunks).times.(the maximum number of conferees to be accommodated in one conference trunk) are needed for conference use, in addition to channels corresponding to telephone sets or CO lines. An attempt has also been made to use economically the channels for conference use, as set forth in Japanese Pat. Pub. Disc. No. 57072/82 gazette, but it still calls for conference use.